The present invention relates to gas turbine engines, and more particularly, to seals for bearing compartments of gas turbine engines.
The rotating shafts and other rotating turbomachinery of gas turbine engines are supported from a non-rotating structure by arrays of anti-friction bearings. In many engines, anti-friction bearings are enclosed in bearing compartments that allow the anti-friction bearings to be more easily lubricated and cooled.
Bearing compartments can be sealed around the shaft by various types of seals including a seal assembly with a carbon seal and a seal plate. The seal plate is mounted on the shaft to rotate therewith and has a contact face which engages and interfaces with the fixed carbon seal. The carbon seal is movable (axially relative to the shaft) against and away from the seal plate by springs and air pressure. Typically, the interfacing surfaces that comprise the contact face of the seal plate and the contact face of the carbon seal are lubricated to minimize friction and wear.
The bearing and other components of the bearing compartment including the carbon seal and the seal plate are cooled and lubricated by oil supplied from other locations in the gas turbine engine. In certain smaller gas turbine models and in locations within the gas turbine where the bearing compartments are disposed in small envelopes with limited space, under-the-bearing race cooling can be utilized to facilitate the transfer of oil to the bearing, and other components of the bearing compartment. The under-the-bearing race cooling thereby avoids the use of a nozzle and saves space within the bearing compartment.
Unfortunately, under-the-bearing race cooling utilizes a plurality of distinct lubricant passages that pass through the seal plate. These distinct lubricant passages in the seal plate result in the contact face of the seal plate experiencing a non-uniform temperature profile along the extent of its circumference (i.e. portions of the contact face disposed near a lubricant passage will have a lower temperature than portions disposed further away from the lubricant passage). The non-uniform temperature profile along the contact face can result in physical warping or distortion of the contact face leading to increased wear of the seal assembly and unwanted amounts of oil passing between the carbon seal and the seal plate out of the bearing compartment.